BA Flight Engineers as pilots
You should remember that all of the BA ex-flight engineers had many years of jet multi-crew flight deck experience, most had some and some had considerable personal flying experience, they had to pass the standard BA pilot selection procedure and the course at Prestwick was integrated (i.e. intense). Sadly some did not make the grade at one stage or another, including type conversion within BA. I think that they would all agree that the courses (PWK & BA) were tough, not least due to the fact that some were in their 40s - age does play a part in your learning ability. Of those who were successful some went on rapidly to command at LGW and even training positions - they were excellent - I know as I trained many onto the 737. A modular course will not adequately prepare you for the rate of progress during training that an operator such as BA will expect. Some years ago BA tried recruiting pilots who had spent years hourbuilding (one took 9 years to achieve 1000hrs), the result was not a success, and a process which my training colleagues & I would not wish to repeat. If considering embarking on a modular course - know what you are getting into & what the major carriers have previously experienced - they cannot afford to make expensive mistakes during the selection process.